1. Field of the Invention
The present invention is related to a method for forming conductive or conjugated polymer film, and more particularly, to a method for forming self-synthesizing organic light emitting diode or polymeric light emitting diode (OLED/PLED) film.
2. Description of the Prior Art
Conventional method for forming transparent, conductive films is to add ITO (indium tin oxide) onto a glass substrate by vacuum evaporation/sputtering, whereby an ITO conductive glass is formed. The ITO glass has the advantage of its firmness, heat resistance, flat surface morphology and good optical features. With these advantages, the ITO glass is largely utilized for the conductive layer of an LCD monitor or a touch pad; however, developments of substitutes are still of great interest due to the weight issue, fragileness, inability to be rolled and high manufacturing costs caused by production of artificial vacuum circumstances. The rollable substrate has gained huge popularity in recent years in that it meets the growing need for small and light products better and that it can be manufactured by the roll-to-roll method which has a relatively low cost. Currently, the rollable substrate is produced by adding ITO onto a polymer substrate by vacuum evaporation/sputtering. However, this method has disadvantages of its own: first of all, the plastic is in general not a good heat-resisting material; second, production of artificial vacuum circumstances is highly costly; and third, the produced conductive or conjugated polymer film has a potential problem of peeling away from the substrate due to the weak adhesion strength between organic and inorganic substances.
The essential elements of an organic light emitting diode include a single layer of light emitting organic semi-conductor deposition between an upper metal cathode and a lower transparent anode. In the traditional way, elements are fabricated on the transparent substrate such as glass, and the transparent anode is made of the transparent conductor of ITO. When a forward bias is applied between the cathode and the anode, electric holes and electrons are introduced into the semi-conductor in the mean time through the cathode and the anode, respectively. The two carriers meet while transferring in the membrane and, when meeting, they generate photons via radiative recombination; the photos then travel all the way out of the system through the transparent cathode and the substrate and give off visible light rays. The underlying mechanism for an organic light emitting diode to emit light is the carrier recombination as mentioned above, thus to improve the efficiency of an organic light emitting diode, one has to balance the introduction rate and the transfer rate of the two carriers(the electric holes and the electrons), so as to improve the efficiency of recombination in the light emitting layer. A common method to achieve this is to take advantage of a multi-layered organic light emitting diode element, wherein a multi-layered organic light emitting diode is structured with an ITO, a hole transporting layer(HTL), an light emitting layer(EML), an electron transport layer(ETL), and metal. However, this multi-layer structure may also have the problem of being flaky due to the weak adhesion strength between organic and inorganic substances.
Accordingly, a new forming process is needed for the conductive or conjugated polymer film, the light emitting membrane and the light emitting layer of an organic light emitting diode (OLED/PLED) in order to equip them with good interfacial adhesiveness and mechanical strength, through which to correspond to industrial utilizations.